feat: US market code 정합성, Telegram 명령 4종, 손절 모니터링 (#132)

- MARKET_SHORTHAND + expand_market_codes()로 config "US" → schedule "US_NASDAQ/NYSE/AMEX" 자동 확장
- /report, /scenarios, /review, /dashboard 텔레그램 명령 추가
- price_change_pct를 trading_cycle과 run_daily_session에 주입
- HOLD시 get_open_position 기반 손절 모니터링 및 자동 SELL 오버라이드
- 대시보드 /api/status 동적 market 조회로 변경

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_db.py

@@ -0,0 +1,60 @@
+"""Tests for database helper functions."""
+
+from src.db import get_open_position, init_db, log_trade
+
+
+def test_get_open_position_returns_latest_buy() -> None:
+    conn = init_db(":memory:")
+    log_trade(
+        conn=conn,
+        stock_code="005930",
+        action="BUY",
+        confidence=90,
+        rationale="entry",
+        quantity=2,
+        price=70000.0,
+        market="KR",
+        exchange_code="KRX",
+        decision_id="d-buy-1",
+    )
+
+    position = get_open_position(conn, "005930", "KR")
+    assert position is not None
+    assert position["decision_id"] == "d-buy-1"
+    assert position["price"] == 70000.0
+    assert position["quantity"] == 2
+
+
+def test_get_open_position_returns_none_when_latest_is_sell() -> None:
+    conn = init_db(":memory:")
+    log_trade(
+        conn=conn,
+        stock_code="005930",
+        action="BUY",
+        confidence=90,
+        rationale="entry",
+        quantity=1,
+        price=70000.0,
+        market="KR",
+        exchange_code="KRX",
+        decision_id="d-buy-1",
+    )
+    log_trade(
+        conn=conn,
+        stock_code="005930",
+        action="SELL",
+        confidence=95,
+        rationale="exit",
+        quantity=1,
+        price=71000.0,
+        market="KR",
+        exchange_code="KRX",
+        decision_id="d-sell-1",
+    )
+
+    assert get_open_position(conn, "005930", "KR") is None
+
+
+def test_get_open_position_returns_none_when_no_trades() -> None:
+    conn = init_db(":memory:")
+    assert get_open_position(conn, "AAPL", "US_NASDAQ") is None